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 *
 * Redistributions of source code must retain the above copyright notice, this
 * list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
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 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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package org.hsqldb.lib;

import java.util.NoSuchElementException;

/**
 * An iterator with an added filter.
 *
 * @author Fred Toussi (fredt@users dot sourceforge.net)
 * @version 2.6.0
 * @since 2.5.1
 */
public class FilteredIterator<E> implements Iterator<E> {

    private final Iterator<E> it;
    private final Filter<E>   filter;
    private E                 nextValue;

    public FilteredIterator(Iterator<E> iterator, Filter<E> filter) {

        this.it     = iterator;
        this.filter = filter;

        moveNext();
    }

    public boolean hasNext() {
        return nextValue != null;
    }

    public E next() throws NoSuchElementException {

        E returnValue = nextValue;

        moveNext();

        return returnValue;
    }

    private void moveNext() {

        while (it.hasNext()) {
            E unfilteredValue = it.next();

            if (filter.test(unfilteredValue)) {
                nextValue = unfilteredValue;

                return;
            }
        }

        nextValue = null;
    }

    public interface Filter<E> {
        boolean test(E object);
    }
}
